1. Field of the Invention
The present invention is directed to an improvement in a vehicle brake mechanism, and more specifically, to a roller retainer for a cam actuated brake assembly.
The invention is particularly useful in a brake assembly of the type disclosed in U.S. Pat. No. 4,206,834. That brake assembly includes a pair of brake shoes having adjacent ends pivotally mounted to a support and a rotatable actuating cam disposed between the other ends of the brake shoes. A roller-type cam follower is provided between each of those other ends of the brake shoes and the actuating cam. The roller-type cam followers are seated in open-ended recesses provided to the brake shoes. Rotary movement of the actuating cam is applied to the roller-type cam followers which causes their respective brake shoes to pivot outwardly about their pivot or anchor pins to contact the inwardly facing friction surface of a brake drum.
The roller-type cam followers are comprised of a stepped cylindrical steel pin having a center portion which bears against the actuating cam and smaller diameter end portions which serve as trunnions seated in open-ended recesses provided to the spaced parallel webs of a dual web brake shoe. Under normal conditions, the roller-type cam follower is trapped between the open-ended recesses provided to the dual web brake shoe and the bearing surface of the actuating cam and held in that arrangement by the brake return spring. However, the brake assembly is comprised of a number of different parts and it is also advantageous to maintain the cam followers in the recesses provided to the brake shoes during assembly and disassembly of the brake mechanism for repair purposes. This limits the number of parts the mechanic has to be concerned with at any given time and the possibility of dropping or misplacing the cam follower rollers.
Means for retaining a roller in the open recesses provided to the ends of a brake shoe is also beneficial during extremely cold weather when the brake shoes may freeze to the surrounding drum and, if and the drum clearance is not properly adjusted and the roller is not retained, the rollers may become displaced from their intended position when the cam is rotated to release the brake.
It is also desirable for assembly and maintenance purposes if the roller retaining means allow the cam-follower rollers to be applied and removed without the use of any tools and without requiring the mechanic to manually move component parts between the cam and the roller followers while the return spring is under tension.
2. Description of the Prior Art
U.S. Pat. No. 3,114,437 disclosed one method of retaining a roller-type cam follower in the open-ended recesses provided to brake shoes. In that patent, the mouth of the open-ended recesses is formed to retain the ends of the rollers and a tool such as a screw driver may be required to remove the rollers from the brake shoes.
Spring means and clip devices have also been employed to retain a roller relative to its brake shoe during transfer and assembly. A spring clip is disclosed in U.S. Pat. No. 3,275,103. Wire spring devices are disclosed in U.S. Pat. No. 2,781,868 and application Ser. No. 306,574 filed on Sept. 28, 1981, as a continuation of Patent Application Ser. No. 108,447 filed on Dec. 31, 1979, now abandoned and assigned to the assignee of the present invention.